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PubMed1997

Specific gas chromatographic analysis of diethylcarbamazine in human plasma using solid-phase extraction.

Diethylcarbamazine (DEC, 1-diethylcarbamyl-4-methylpiperazine) is an antiparasitic piperazine derivative used in the treatment of lymphatic filariasis. DEC-N-oxide is a major metabolite in humans which has antifilarial activity. Gas chromatographic analysis of DEC in plasma can be complicated by the presence of the metabolite, since the thermally unstable DEC-N-oxide is converted to a material which coelutes with DEC under the conditions of the analysis. We now report a method to separate DEC-N-oxide from DEC in plasma using solid-phase extraction with subsequent gas chromatographic analysis using a nitrogen specific detector. 1-Diethylcarbamyl-4-ethylpiperazine (E-DEC) was the internal standard. The standard curve of DEC is linear in the range of 10 to 200 ng/ml. The limit of detection is 4 ng/ml. Reproducibility at 10, 100 and 200 ng/ml concentration points of the standard curve gives coefficients of variation of 6.1%, 7.8% and 1.6%, respectively. Recovery following solid-phase extraction is 99.3% for DEC and 94.8% for the internal standard. This sensitive and specific analytical method is suitable for pharmacokinetic studies of DEC.

Calorimetry, Differential Scanning↗

PubMedDate not supplied

Analysis of phenothiazines in human body fluids using disk solid-phase extraction and liquid chromatography.

Seven phenothiazine derivatives, perazine, perphenazine, prochlorperazine, propericiazine, thioproperazine, trifluoperazine, and flupentixol, have been found to be extractable from human plasma and urine samples using disk solid-phase extraction (SPE) with an Empore C18 cartridge. Human plasma and urine (1 mL each) containing the 7 phenothiazine derivatives were mixed with 2 mL of 0.1M NaOH and 7 mL distilled water and then poured into the disk SPE cartridges. The drugs were eluted with 1 mL chloroform- acetonitrile (8 + 2) and determined by liquid chromatography with ammonium formate/formic acid-acetonitrile gradient elution. The detection was performed by ultraviolet absorption at 250 nm. The separation of the 7 phenothiazine derivatives from each other and from impurities was generally satisfactory using a SymmetryShield RP8 column (150 x 2.1 mm id, 3.5 microm particle size). The recoveries of the 7 phenothiazine derivatives spiked into plasma and urine samples were 64.0-89.9% and 65.1-92.1%, respectively. Regression equations for the 7 phenothiazine derivatives showed excellent linearity, with detection limits of 0.021-0.30 microg/mL for plasma and 0.017-0.30 microg/mL for urine. The within-day and day-to-day coefficients of variation for both samples were commonly below 9.0 and 14.9%, respectively.

Acetonitriles↗

PubMed2003

Simultaneous determination of nimesulide and hydroxynimesulide in rat plasma, cerebrospinal fluid and brain by liquid chromatography using solid-phase extraction.

A liquid chromatographic method with UV detection for the quantification of nimesulide (N) and hydroxynimesulide (M1) in rat plasma, cerebrospinal fluid (CSF) and brain tissue is reported. Plasma samples (250 microl) and brain homogenates added with the right amount of the internal standard (I.S., 2'-(cyclohexyloxy)-4'-nitrophenyl methanesulphonanilide, NS398) are extracted on C(18) disposable cartridges by solid-phase extraction (SPE), while CSF samples are analyzed without any extraction. The separation is performed at room temperature on a Waters Symmetry C(18) 3.5 microm (150x4.6 mm I.D.) column with acetonitrile-sodium citrate buffer pH 3.00 (53:47, v/v) as mobile phase, at a flow-rate of 1.1 ml/min and detection at 240 nm. The retention times are 3.3, 6.0 and 9.9 min for M1, N and I.S., respectively. The lower limits of quantitation for either nimesulide and M1 are 25 ng/ml for plasma, 20 ng/ml for CSF and 25 ng/g for brain tissue. The calibration curves are linear up to 10,000 ng/ml for plasma, 5000 ng/ml for CSF and 5000 ng/g for brain tissue. This new assay can be applied to the study of the role of nimesulide in the modulation of neuroinflammatory processes.

Animals↗

PubMed2004

Detection and identification of phenazone-type drugs and their microbial metabolites in ground and drinking water applying solid-phase extraction and gas chromatography with mass spectrometric detection.

A new analytical method applying in situ derivatization was developed to enable the extraction of polar drug metabolites from water samples by solid-phase extraction (SPE). An additional derivatization by silylation was used to enhance the sensitivity of analyte detection by gas chromatography-mass spectrometry (GC-MS). Thus, the two metabolites 1,5-di-methyl-1,2-dehydro-3-pyrazolone (DP) and 4-(2-methylethyl)-1,5-dimethyl-1,2-dehydro-3-pyrazolone (PDP), postulated for the degradation of phenazone and propyphenazone, were identified and detected up to the microg/L level in raw and drinking water samples from public water supply.

Acetylation↗

PubMed1997

High-performance liquid chromatographic method for determination of DX-9065a, a novel anticoagulant, in human urine and feces using cation-exchange solid-phase extraction.

A simple HPLC method for determination of DX-9065a in human urine and feces was developed. The drug was extracted by Bond Elut CBA, a cation-exchange solid-phase extraction cartridge. The extracted drug was analyzed by HPLC with UV detection at 242 nm. With this extraction procedure, no interfering peaks were observed. The method developed was validated and showed adequate precision and accuracy. This method was applied to human clinical samples obtained from healthy Japanese volunteers who had orally received the drug. Using this method, the excretion profile of the drug in human after oral administration was revealed for the first time.

Anticoagulants↗

PubMed1991

Separation of cholesterol esters by silver ion chromatography using high-performance liquid chromatography or solid-phase extraction columns packed with a bonded sulphonic acid phase.

Two methods for the separation of cholesterol esters, based on the number of double bonds in their fatty acid moieties, are presented. Silver ion chromatography, usually performed on thin-layer chromatographic plates, was made suitable for high-performance liquid chromatography (HPLC) and solid-phase extraction. Separation on a bonded sulphonic acid phase loaded with silver ions was achieved with cholesterol esters containing up to six double bonds in their fatty acid moieties. No cross-contamination between fractions with different numbers of double bonds was detected with the HPLC method, was demonstrated by subsequent gas chromatographic analysis of the fatty acid moieties, following transmethylation. For adequate separations with the solid-phase extraction columns it proved important to avoid overloading. The methods may be of use for the off-line analyses of the sterol compositions of the isolated fractions, which each contain sterol esters with an equal number of double bonds in their fatty acid moieties.

Animals↗

PubMed2004

[Study on solid-phase-extraction spectrophotometric determination of silver with p-sulfobenzylidene-rhodanine].

The color reaction of silver with p-sulfobenzylidene-rhodanine (SBDR) was studied. Based on the color reaction of SBDR with silver (I) and the solid phase extraction of its colored complex with Waters Porapak Sep-Park-C18 cartridge, a new method for the determination of micro-amount of silver (I) was studied. In the presence of pH = 2.8 citric acid-sodium hydroxide buffer solution and Tween-80 medium, SBDR can react with silver (I) to form a stable 2:1 complex. The colored complex can be extracted by C18 cartridge and eluted by ethanol (containing 5% acetic acid), and then can be determined by spectrophotometry. The molar absorptivity is 7.53 x 10(4) L x mol(-1) x cm(-1) at 520 nm. Beer's law is obeyed in the range of 0-1.2 microg x (25 mL)(-1). This method can be applied to the determination of silver in water with satisfactory results.

Environmental Monitoring↗

PubMed2005

Determination of amphetamine, methamphetamine, 3,4-methylenedioxyamphetamine, 3,4-methylenedioxyethylamphetamine, and 3,4-methylenedioxymethamphetamine in urine by online solid-phase extraction and ion-pairing liquid chromatography with detection by electrospray tandem mass spectrometry.

A method using an online solid-phase extraction (SPE) and ion-pairing liquid chromatography with electrospray tandem mass spectrometry (LC/ES-MS/MS) was developed for determination of amphetamine (Amp), methamphetamine (mAmp), 3,4-methylenedioxyamphetamine (MDA), 3,4-methylenedioxyethylamphetamine (MDEA), and 3,4-methylenedioxymethamphetamine (MDMA) in urine samples. A SPE cartridge column with both hydrophilic and lipophilic functions was utilized for online extraction. A reversed-phase C18 LC column was employed for LC separation and MS/MS was used for detection. Trifluoroacetic acid was added to the mobile phase as an ion-pairing reagent. This method was fully automated and the extraction and analysis procedures were controlled by a six-port switch valve. Recoveries ranging from 85-101% were measured. Good linear ranges (10-500 ng/mL) for Amp and mAmp were determined. For MDA, MDMA and MDEA, dual linear ranges were obtained from 5-100 and 100-500 ng/mL, respectively. The detection limit of each analytical compound, based on a signal-to-noise ratio of 3, ranged from 1-3 ng/mL. The applicability of this newly developed method was examined by analyzing several urine samples from drug users. Good agreement was obtained between the results from this method and a literature GC/MS method.

Amphetamines↗

PubMed1996

High-performance liquid chromatographic analysis for the determination of miconazole in human plasma using solid-phase extraction.

A high-performance liquid chromatographic method for the determination of miconazole in human plasma is described. A solid-phase extraction was performed on an octadecyl (C18) cartridge. Miconazole was eluted with methanol, separated on a reversed-phase column and was measured by ultraviolet detection at 230 nm. The absolute extraction recovery from plasma samples was 85%. The limit of detection was established as 5 ng/ml. The coefficient of variation of the determination of plasma levels by this method over the standard curve concentration range was less than 10%, except with the concentration of 10 ng/ml. The plasma levels of miconazole in twelve healthy volunteers given a 250-mg oral dose of two tablet forms were determined by this method.

Adult↗

PubMed1990

Application of solid-phase extraction to the isolation and determination of paracetamol and its metabolites.

A series of clean-up columns for solid-phase extraction (SPE) were packed with various C18 phases of different physico-chemical surface properties. These SPE columns were used for the isolation and determination of paracetamol and its metabolites from biological samples. The packing with a monomeric structure of chemically bonded phase showed the best recovery of tested substances in urine.

Acetaminophen↗

PubMed1993

An investigation of the effects of carbon loading and endcapping on the solid-phase extraction of beta-blockers onto C18 bonded silica gel.

The effects of carbon loading and endcapping on the solid-phase extraction onto C18 bonded silica gel of a range of beta-blockers from aqueous buffer and from dog plasma has been investigated. The highest extraction efficiencies were obtained for those phases with carbon loadings of between 5 and 16% for phases without endcapping or 10.5-14% for endcapped material. With carbon loadings of 18 and 22% (plus endcapping) poor extractions from the matrix were obtained combined with further losses at the wash steps. Matrix effects were observed with dog plasma which accentuated the effects seen with buffer. These results are best explained by assuming that a cationic interaction of the secondary amino group present in the analytes with residual silanols on the silica surface is primarily responsible for the extraction of these analytes.

Adrenergic beta-Antagonists↗

PubMed2004

Continuous solid-phase extraction and gas chromatographic determination of organophosphorus pesticides in natural and drinking waters.

A simple, rapid continuous-flow solid-phase extraction method with gas chromatographic detection for the determination of organophosphorus pesticides is proposed. The continuous system consists of an adsorbent column where pesticides are preconcentrated and subsequently eluted with ethyl acetate. Various sorbent materials were assayed of which RP-C18 was found to provide the best results, with a sorption efficiency close to 100%. A comparative study of the determination of pesticides in aqueous samples was conducted using gas chromatography with nitrogen-phosphorus (NPD) and flame ionization (FID) detection. The detection limits of the method for 10 ml of sample were between 50-130 ng/l and 4.5-1 1.7 microg/l with NPD and FID detection, respectively. The method was used to determine organophosphorus pesticides in river, pond, well and tap waters, all with good precision (2.9-4.3%) and recoveries ranging from 93.8 to 104.5%.

Chromatography, Gas↗

PubMed2004

Optimization of solid-phase extraction for a liquid chromatographic-tandem mass spectrometric general unknown screening procedure by means of computational techniques.

A solid-phase extraction (SPE) method was optimized to suit the particular demands of an information-dependent acquisition LC-MS-MS procedure for general unknown screening in a forensic toxicology setting. In a first phase, a Plackett-Burman screening design with fold-over was carried out to distinguish the significant factors affecting the extraction procedure. This part eventuated in the determination of only three statistically relevant parameters, requiring consecutive optimization. To that end, in phase II of this study, a rotatable central composite design was applied to define the response surface as a function of the significant parameters and to choose the optimal conditions for the SPE.

Chromatography, Liquid↗

PubMed2005

Simple solid-phase extraction method for determination of polychlorinated biphenyls and selected organochlorine pesticides in human serum.

A simple off-line solid-phase extraction (SPE) method for isolation of polychlorinated biphenyls (PCBs) and selected organochlorine pesticides (OCPs) from human serum has been developed. The procedure includes denaturation of serum proteins by a mixture of water-1-propanol, application of the sample by aspiration twice repeatedly through the SPE column and elution with a mixture of n-hexane-dichlormethane. After final clean-up the compounds of interest were analysed by gas chromatography with micro-electron capture detection (GC-microECD). The recoveries achieved for PCB congeners using spiked porcine serum samples were 99-120% and for OCPs 88-115%. Relative standard deviations (RSD) ranged from 3 to 7%. The method was applied to real human serum samples and the recoveries of analytes in the serum were proportionally recalculated considering the recovery of the internal standard PCB-174. PCB-103 served as a syringe standard to correct volume of samples analysed. The aim of this study was to develop an effective off-line SPE procedure by optimization of existing SPE methods to supply laborious, solvent- and time-consuming liquid-liquid extraction (LLE) in routine analytical process.

Animals↗

PubMed2005

Solid-phase extraction coupled with liquid chromatography-tandem mass spectrometry for determination of trace rosiglitazone in urine.

This project evaluated solid-phase extraction (SPE) combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS) to determine the trace amount of rosiglitazone in human urine. The analytical performance of four modes of LC-MS and tandem MS operation (atmospheric pressure chemical ionization (APCI), electrospray ionization (ESI), positive and negative ionization) was compared for two mass spectrometers, a triple-quadrupole and a quadrupole ion trap instrument. Rosiglitazone was extracted from urine using a SPE cartridge of 50mg C8 sorbent and acetonitrile used as the eluting solvent. Samples were then separated on a RP18 column interfaced with a tandem mass spectrometer. The recovery of rosiglitazone was greater than 91.2%. The urine assay combining SPE and LC-APCI-MS/MS of triple-quadrupole was proved a very selective and sensitive method for determination of trace rosiglitazone. The assay was linear over a wide range, with a lower limit of quantification of 0.1 ng/mL using 1 mL of urine. The intra- and inter-day precisions were <9.8% and <7.9%, respectively, and the accuracies were in the range 91.0-103.6%. The rosiglitazone concentration profile in human urine was also determined. The results of this study reveal the adequacy of SPE-LC-APCI-MS/MS method for analyzing rosiglitazone from diabetic patients' urines. The concentrations of rosiglitazone were detected to range from 760 to 164 pg/mL.

Administration, Oral↗

PubMed2000

Quantitation of nifedipine in human plasma by on-line solid-phase extraction and high-performance liquid chromatography.

An analytical methodology for nifedipine quantitation in plasma by on-line solid-phase extraction (SPE) and high-performance liquid chromatography (HPLC) is described. The SPE cartridges contain C2 and the analytes nifedipine and nitrendipine (internal standard) are separated on a C18 column with a mobile phase consisting of acetonitrile-13 mM phosphate buffer pH 7 (65:35, v/v) followed by UV detection at 338 nm. Validation of the method demonstrated good recoveries (>90%), sensitivity (limit of quantification, 2 ng/ml), based on a 500 microl sample volume, accuracy and precision (<5.5% in concentrations greater than the limit of quantitation). This methodology has been used for bioequivalence studies.

Calcium Channel Blockers↗

PubMed2000

Tandem solid-phase extraction of atrazine ozonation products in water.

The preconcentration of aqueous solutions containing atrazine degradation products was investigated using solid-phase extraction on octadecyl and cation-exchanger silica phases. The retention and elution steps were studied and evaluated separately in order to define and optimize the critical experimental parameters involved. A strategy which combines sequentially both phases is proposed to fractionate compounds into two groups of increasing polarities: firstly, the native pesticide, hydroxyatrazine and most chlorotriazines on octadecyl support, and secondly monodealkylated hydroxytriazines, ammeline and ammelide on cation-exchanger. This tandem procedure was successfully applied for analysing and quantifying atrazine ozonation products and its efficiency demonstrated using [U-ring 14C]-labelled atrazine experiments.

Atrazine↗

PubMed2001

Improvement of ethyl glucuronide determination in human urine and serum samples by solid-phase extraction.

An improved method for the determination of ethyl glucuronide (EtG) in human serum and urine was developed using solid-phase extraction (SPE) and gas chromatography (GC) with mass spectrometric detection (MS). EtG was isolated from serum and urine using aminopropyl SPE columns after deproteination with perchloric acid and hydrochloric acid, respectively. The chromatographic separation was performed on a DB 1701 fused-silica column. At a signal-to-noise ratio of 3:1, a quantification limit of 173 and 560 ng/ml and a detection limit of 37 and 168 ng/ml could be determined for serum and urine, respectively. This indicates high specificity and sensitivity of the described method. The mean absolute recovery was approximately 85%, while intra- and inter-day precision of the assay were all less than 7.5%. The linearity of the calibration curves was satisfying as indicated by correlation coefficients of >0.993. The presented method provides the basis for determination and identification of EtG in human serum and urine samples in a low-concentration range for monitoring alcohol consumption during treatment for alcohol dependence and comorbid alcohol abuse of psychotherapy patients.

Calibration↗